In many aircraft, air is extracted from the main engines to supply conditioned air for various aircraft pneumatic systems throughout the aircraft. Aircraft employing this technique include aircraft that are powered by turbo-jet, turbo-fan, and turbo-prop engines, such as, commercial air transport aircraft, business jets, and military aircraft. The air extracted from the main engines is referred to as “bleed air,” and is supplied to and controlled by a bleed air system (BAS). The BAS generally comprises a series of valves, ducting, and a pre-cooler, and the bleed air is sourced from a fan and/or different ports of the compressor section of a turbine engine. Air in the BAS is generally supplied at high pressure and high temperature, and is then regulated and cooled before it is delivered downstream to the aircraft pneumatic systems.
The valves in the BAS need to open, close, regulate and modulate against varying inlet (upstream) air pressures, in order to maintain the desired output (downstream) pressures. Most valves in the BAS are controlled by actuators, many of which are also pneumatically controlled. In operation, bleed air may be routed to a pneumatic actuator in which a piston or a diaphragm is pressurized to move a valve in a flow path of a flow body such as a duct. The valve may take a variety of forms suitable for performing the described functions.
Fan air valves are valves in the BAS that face several specific issues. First, the high airflow subjects the fan air valve in the BAS to a tremendous amount of torque. In particular, the torque on the fan air valve may make the fan air valve difficult to control. In order to reduce the torque on the fan air valve, the upstream surface of the fan air valve may be modified with one or more strategically placed standoffs. The standoffs are placed at predetermined locations around the upstream surface to create a torque reducing fan air valve. Secondly, the fan air is often cold enough to cause an ice buildup on an upstream surface of the torque reducing fan air valve. However, when the torque reducing fan air valve is modulated open, one or more of the standoffs may interact with the ice buildup. The continued modulation of the torque reducing fan air valve may cause the standoff to compress the ice buildup near the perimeter of the fan air valve. It has been postulated that this ice buildup could cause the valve to stick, and thereby reduce the reliability of the torque reducing fan air valve. Attempts to address this postulated issue generally include not completely closing the torque reducing fan air valve, which results in not completely closing off the airflow in the respective duct when full closure is desired, and employing additional software and components to prevent ice buildup.
Hence, design improvements to torque reducing fan air valves that minimize or eliminate compression of the ice buildup are desirable. An improved torque reducing fan air valve (hereinafter referred to as a fan air valve, or valve, for simplicity) would also be one that could completely close off the airflow in the respective duct when full closure is desired. The present invention addresses at least these needs.